chainntnfs/neutrinonotify: fix early historical confirmation dispatch

In this commit, we fix an existing bug within the logic of the neutrino
notifier. Rather than properly dispatching only once a transaction had
reached the expected number of confirmations, the historical dispatch
logic would trigger as soon as the transaction reached a single
confirmation.

This was due to the fact that we were using the scanHeight variable
which would be set to zero to calculate the number of confirmations.
The value would end up being the current height, which is generally
always greater than the number of expected confirmations. To remedy
this, we’ll now properly use the block height the transaction was
originally confirmed in to know when to dispatch.

This also applies a fix that was discovered in
93981a85c0.

chainntnfs/neutrinonotify/neutrino.go

@@ -419,10 +419,7 @@ func (n *NeutrinoNotifier) attemptHistoricalDispatch(msg *confirmationsNotificat
 
 	targetHash := msg.txid
 
-	var (
-		confDetails *chainntnfs.TxConfirmation
-		scanHeight  uint32
-	)
+	var confDetails *chainntnfs.TxConfirmation
 
 	chainntnfs.Log.Infof("Attempting to trigger dispatch for %v from "+
 		"historical chain", msg.txid)
@@ -503,20 +500,21 @@ chainScan:
 	// Otherwise, we'll calculate the number of confirmations that the
 	// transaction has so we can decide if it has reached the desired
 	// number of confirmations or not.
-	txConfs := currentHeight - scanHeight
+	txConfs := currentHeight - confDetails.BlockHeight + 1
 
 	// If the transaction has more that enough confirmations, then we can
 	// dispatch it immediately after obtaining for information w.r.t
 	// exactly *when* if got all its confirmations.
 	if uint32(txConfs) >= msg.numConfirmations {
+		chainntnfs.Log.Infof("Dispatching %v conf notification, "+
+			"height=%v", msg.numConfirmations, currentHeight)
 		msg.finConf <- confDetails
 		return true
 	}
 
 	// Otherwise, the transaction has only been *partially* confirmed, so
 	// we need to insert it into the confirmation heap.
-	confsLeft := msg.numConfirmations - uint32(txConfs)
-	confHeight := uint32(currentHeight) + confsLeft
+	confHeight := confDetails.BlockHeight + msg.numConfirmations - 1
 	heapEntry := &confEntry{
 		msg,
 		confDetails,
@@ -524,7 +522,7 @@ chainScan:
 	}
 	heap.Push(n.confHeap, heapEntry)
 
-	return false
+	return true
 }
 
 // notifyBlockEpochs notifies all registered block epoch clients of the newly
@@ -574,6 +572,9 @@ func (n *NeutrinoNotifier) notifyConfs(newBlockHeight int32) {
 	nextConf := heap.Pop(n.confHeap).(*confEntry)
 	for nextConf.triggerHeight <= uint32(newBlockHeight) {
 
+		chainntnfs.Log.Infof("Dispatching %v conf notification, "+
+			"height=%v", nextConf.numConfirmations, newBlockHeight)
+
 		nextConf.finConf <- nextConf.initialConfDetails
 
 		if n.confHeap.Len() == 0 {